A river is a natural waterway on the Earth's surface, which channels freshwater from the mountains to the sea.
Rivers begin as small trickles of water up in the mountains. This is its source, and it eventually forms a small stream which then flows down the mountain. The water erodes the land, carving a bigger channel and forms the main river.Upstream areas are characterized by steep V-shaped valleys, waterfalls, and fast flowing water among boulders and rocks. In the middle part, the river winds its way slowly through the flatter land, and continues to widen its channel by meandering and depositing material that is too heavy to carry in the water. As it makes its way out to the sea, it flows even more slowly and starts to deposit even more material in and around its own channel. At its mouth, where the river meets the sea, there is a sudden drop in velocity, and all the material that was being carried in the water column is deposited right there. As the material builds up from continuous deposition, the mouth of the river gets blocked and the river has to find new outlets into the sea by carving new streams wherever it can. This is the formation process of a delta and is characteristic of all river mouth areas.
"Rivers in Malaysia"
There are 189 river basin systems with about 1800 rivers in Malaysia. The total length of the rivers is estimated to be 38,000km. Most of the rivers in Peninsular Malaysia originate from the central mountain ranges. East Malaysia contains the country’s two longest rivers: the Rajang in Sarawak and the Kinabatangan in Sabah. They are each 560km (350mi) long and navigable for part of their courses. Peninsular Malaysia’s longest rivers include the Pahang (470km/290mi long), the Kelantan (about 400km/250mi long), and the Perak (about 240km/150mi long).
The major role of rivers today is to provide clean water for the 25 million people currently living in Malaysia. Among the river basins, 30 of them are reservoirs and they supply 97% of the water supply throughout Malaysia. Despite the importance of rivers as our main source of drinking water, many of our urban rivers today are heavily polluted with all sorts of chemicals and rubbish due to unsustainable development and improper management of rivers. Only 50% of our rivers remain ‘clean’, while the other 50% are polluted or considered ‘dead’ rivers.
What is a "River Basin"?
A river basin is the entire area drained by a river including its tributaries. That means, all water in the river basin area drains into the river and its tributaries. Therefore, the flow of water sets the boundaries of a river basin.
Hydrologists sometimes refer to river basins as catchments or drainage basins. The term watershed is use synonymously with river basin, especially in the U.S.
River basins catch precipitation and accumulate water, which flows across or under the landscape. They come in many different shapes and sizes. River basins can be hilly, mountainous, or nearly flat and can be comprised of many land uses including forests, farms, towns and cities.
